Determination of radiative neutron capture cross sections for unstable nuclei by Coulomb dissociation

H. Utsunomiya (Konan University)

Outline

1. Methodology of the SF method

2. Applications with real photons

3. Applications with virtual photons

RIKEN Seminar Nov. 1, 2011

Collaborators

H. Utsunomiyaa) , H. Akimunea) , T. Yamagataa) , H. Toyokawac) , H. Haradad), F. Kitatanid) ,Y. -W. Luie) ,S. Gorielyb) I. Daoutidisb) , D. P. Arteagaf) , S. Hilaireg) , and A. J. Koningh)

a) Department of Physics, Konan University, Japanb) Institut d’Astronomie et d’Astrophysique, ULB, Belgiumc) National Institute of Advanced Industrial Science and Technology, Japan d) Japan Atomic Energy Agency, Tokai, Naka-gun, Ibaraki 319-1195, Japane) Cyclotron Institute, Texas A&M University, USA f) Institut de Physique Nucléaire, Université Paris-Sud, France g) CEA,DAM, DIF, Arpajon, Franceh) Nuclear Research and Consultancy Group, The Netherlands

Radiative neutron capture cross sectionsfor unstable nuclei in nuclear astrophysics

Direct measurements at CERN n-TOF, LANSCE-DANCE, Frankfurt-FRANZ and J-Parc ANNRI facilities

can target some of unstable nuclei along the valley of -stability if samples can be prepared. ---> s-process

Indirect experimental method is called in for unstable nuclei along the valley of -stability ---> s-process neutron-rich region ---> r-process

surrogate reaction technique ANY OTHER?

follows the statistical model of the radiative neuron capture in the formation of a compound nucleus and its decay by using experimentally-constrained SF.

-ray strength function methodH. Utsunomiya et al., PRC80 (2009)

n + AX

A+1X

E, J,

AX(n,)A+1XRadiative neutron capture

continuum

SF NLD

decay process

n(E) kn

2 gJ

T(E,J, ) Tn (E,J, )

TtotJ ,

T(E,J,) TX ()

,X , TX () (E )d

X ,

Total transmission coefficient

€

TXλ (εγ ) = 2π ΓXλ /D

fXλ (εγ ) ↓= εγ−(2λ +1)

ΓXλ (εγ )

D

-ray strength function nuclear level density

(E )X=E, M=1, 2, …

SF method

neutron resonance spacinglow-lying levelssource of uncertainty

Hauser-Feshbach model cross section for AX(n,)A+1XHauser-Feshbach model cross section for AX(n,)A+1X

After integrating over J and π

-ray strength function: nuclear statistical quantity interconnecting (n,) and (,n) cross sections

in the HF model calculation

n+AX

A+1X

E, J, AX(n,)A+1X

€

fXλ (ε γ ) ↓= ε γ−(2λ +1)

ΓXλ (ε γ )

D

A+1X(,n)AX

fX ()

21

(hc)2

Xabs()

2 1

Photoneutron emissionRadiative neutron capture

fX () fX () Brink Hypothesis

Xn () X

abs() Tn

Tn T

continuum

€

fXλ (ε γ )

Sn

Sn

SnGDR

PDR, M1

Structure of -ray strength function

Primary strength E1 strength in the low- energy tail of GDR

Extra strengths

6 – 10 MeV

SnGDR

PDR, M1

(,n)(,’)

Particle- coin.

CDOslo method

R. Schwengner R. Schwengner

A. Zilges A. Zilges

M. Guttormsen M. Guttormsen

(p,p’)A. TamiiP. von Neumann-CoselA. TamiiP. von Neumann-Cosel

A. Tonchev A. Tonchev

Sn

(,n) GDR

Methodology of SF method

STEP 1

Measurements of (,n) c.s. near Sn

A-1A-1 AA

(,n) SFSTEP 1

Sn

Methodology of SF method

STEP 2

Normalization of SF

Extrapolation of SF by models

Sn

(,n) GDR

A-1A-1 AA

(,n) SFSTEP 1

JUSTIFICATION BY REPRODUCING KNOWN (n,) C.S.

Methodology of SF method

STEP 2

known (n,)

SnSn

(,n) GDR

A-1A-1 AA

(,n) SFSTEP 1

neutron capture byunstable nucleus

Methodology of SF method

STEP 3

(n,) to be deduced

A+1A+1 A+2A+2

(,n)

STEP 3

A+1X(n,)A+2X

known (n,)

A-1A-1 AA

(,n)

STEP 1STEP 2

Extrapolation is made in the same way as for stable isotopes.

(,n) GDR

Sn

STEP 1STEP 2

66Sn 116 117 118 119 12012127 h 122

123129 d 124

105 106 1076.5 106 y 108Pd

90 91 92 931.53 106 y 94

9564 d 96Zr

77 78 792.95 103 y 80Se 76 75

120 d

89 3.27 d

104

66115

Applications LLFP (long lived fission products) nuclear waste

Astrophysical significancePresent (,n) measurementsExisting (n,) data

7

3

5

4

H.U. et al., PRC82 (2010)

H. Utsunomiya et al., PRC80 (2009)

H.U. et al., PRL100(2008) PRC81 (2010)

To be published

(n,) c.s. to be deduced

EE

L

L L e

1 1cos cos

e

e

E

L

Ee

•• EnergyEnergy

Laser Electron Beam

Inverse Compton Scattering

= Ee/mc2

“photon accelerator”

Laser Compton scattering -ray beam

=1064, 532 nm

AIST (National Institute of Advanced Industrial Science and Technology)

Detector System

Triple-ring neutron detector20 3He counters (4 x 8 x 8 ) embedded in polyethylene

90 91 92 931.53 106 y 94

9564 d 96Zr 89

3.27 d

ApplicationsLLFP (long lived fission products) nuclear waste

Astrophysical significance

Present (,n) measurements

5

Measurements of (,n) cross sections

Justification of SF with existing (n,) data

STEP 1

STEP 2 Investigation of SF that reproduces (,n) cross sections

Extrapolation of SF below Sn

STEP 3 Prediction of (n,) cross sections for 93Zr and 95Zr

STEP 1 – (,n) 断面積の中性子しきい値近傍での高精度測定

91Zr

92Zr

94Zr

96Zr

Application STEP 2 – Extrapolation of SF to the low-energy region

HFB+QRPA E1 strength supplemented with a giant M1 resonance in Lorentz shape

Eo ~ 9 MeV, ~ 2.5 MeV, o ~ 7 mb

~ 2% of TRK (Thomas-Reiche-Kuhn) sum rule of GDR

HFB+QRPA+ Giant M1

92Zr

Application STEP 2 – Justification of the adopted SF

TALYS code of the HF model

Application STEP 2 – Justification of the adopted SF

93Zr[T1/2=1.5×106 y]

Results for Zr isotopes

long-lived fission product nuclear waste

95Zr[T1/2=64 d] s-process branching

30-40% uncertainties

Comparison with the surrogate reaction techniqueForssèn et al., PRC75, 055807 (2007)

93Zr(n,)94Zr

95Zr(n,)96Zr

1. The surrogate reaction technique gives larger cross sections by a factor of ~ 3 than the SF method.

The surrogate reaction technique gives similar cross sections to those given by the SF method provided that a choice is made of the Lorentian type of SF.

Zr isotopes

66Sn 116 117 118 119 12012127 h 122

123129 d 12466115

Applications

7

STEP 1 Measurement of (,n) cross sections

Sn isotopes

H. Utsunomiya et al., PRC80 (2009)

HFB+QRPA E1 strength supplemented with a pygmy E1 resonance in Gaussian shape

Eo ~ 8.5 MeV, ~ 2.0 MeV, o ~ 7 mb

~ 1% of TRK sum rule of GDR

STEP 2 – Extrapolation of SF to the low-energy region

HFB+QRPA+ PDR

SF for Sn isotopes

Toft et al., PRC 81 (2010)PRC 83 (2011)

Comparison with the Oslo method

STEP 2 – Justification of the extrapolated SF

STEP 3 – Statistical model calculations of (n,) cross sections for radioactive nuclei

121Sn[T1/2=27 h]

123Sn[T1/2=129 d]

Uncertainties: 30-40%

Uncertainties: a factor of 3

105 106 1076.5 106 y 108Pd 104

ApplicationsLLFP (long lived fission products) nuclear waste

Astrophysical significance

3

STEP 1 Measurement of (,n) cross section

Pd isotopes

SF for 108Pd STEP 2 – Extrapolation of SF

RMF + QRPA D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008)

Sn

STEP 2 – Justification of the extrapolated SF

D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008).

S. Goriely, Phys. Lett. B436, 10 (1998). Hybrid

Deformed RRPA

107Pd[T1/2=6.5×106 y] long-lived fission product nuclear waste

30-40% uncertainties stem from NLD

79Se(n,)80Se

77 78 792.95 103 y 80Se 76 75

120 d4

F. Kitatani (JAEA) a systematic measurement for stable Se isotopes ---> complete application of SF method To be published

A. Makinaga et al, PRC79 (2009)Large uncertainties has remained because of a lack of

justification in STEP 2.

s-process nucleosynthesis and stellar models

€

A NA

€

A€

A = σv /vT

€

vT =2kT

μn

⎛

⎝ ⎜

⎞

⎠ ⎟

1/ 2

Main componentMain componentWeak componentWeak component

Zr 〜 BiFe 〜 Zr

MainMainWeakWeak

Zr

AGB stars （ 1 ≤M≤ 3 ）He-shell burning

Massive stars （ 8 ≤ M ）Core He burning

Carbon burning12C(12C,n)23MgkT ≈ 91 keVnn≈1011 cm-3

22Ne(,n)25Mg kT=26 keV, nn≤106 cm-3

13C(,n)16O kT=8 keV, nn≈107 cm-3

22Ne(,n)25Mg kT=23 keV, nn≤1011 cm-3

(E): E ： 0.3 〜 300 keV

MACS

s-process branching nuclei

F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)

s-only nuclei

The s-process branching is a good measure of the stellar neutron density and temperature.

151Sm(n,) @ n-TOF (CERN)

Sm2O3, 89.9% 151Sm, 206.4 mg

Normal applications of the SF method with real photons requires at least 2 neighboring stable isotopes.

s-process branching nuclei

F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)

９ branching nuclei

63Ni79Se

81Kr, 85Kr95Zr

147Nd151Sm153Gd185W

(n,) to be deduced

A+1A+1 A+2A+2

(,n)

known (n,)

A-1A-1 AA

(,n)

s-process branching nuclei

F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)

Some s-process branching nuclei have only one stable isotope.

stable133Cs159Tb165Ho169Tm181Ta203Tl

branching134,135Cs160Tb163Ho170,171Tm179Ta204Tl

8 branching nuclei

• Some s-process branching nuclei have 2 stable isotopes that are not neighboring to each other.

s-process branching nuclei

s-only nuclei3 branching nuclei

stable151,153Eu

branching152,154,155Eu

Coulomb dissociation experiments with SAMURAI at RIKEN-RIBF

s-process branching nuclei halflife(yr)

Coulomb dissociation (n,) data

134Cs,135Cs 2.0652, 2.3×

106 136Cs,135Cs,134Cs 133Cs

152Eu* 13.537 153Eu, 152Eu 151Eu

154Eu,155Eu 8.593, 4.753 156Eu,155Eu,154Eu 153Eu

160Tb 0.198 161Tb,160Tn 159Tb

163Ho 4570 164Ho,166Ho 165Ho

170Tm,171Tm 0.352, 1.921

172Tm,171Tm,170Tm 169Tm

179Ta 1.82 180Ta,182Ta 181Ta

204Tl 3.78 205Tl,204Tl 203Tl

11 branching nuclei 18 Coulomb dissociations

Ambitious application of the SF method to the r-process

The significance is controversial ！ BUT this would be the first application to a very neutron-rich

nucleus.

A pioneering work is in progress.1) A systematic study of the SF for Sn isotopes116Sn ,…., 124Sn (7 stable) → → → 132Sn

132Sn(,n) data: GSI Coulomb dissociation data for 132Sn

131Sn(n,)132Sn cross sections in the r-process nucleosynthesis

New -ray Beam Line @ NewSUBARU

Summary

SF method: (n,) c.s. for unstable nuclei1. Nuclear Experiment: (,n) c.s. real photons for stable nuclei virtual photons for unstable nuclei (CD) 　　　　　 2. Nuclear Theory: models of SF models of NLD primary strength: low-energy E1 of GDR extra strengths: PDR, M1

3. Coulomb dissociation experiments with SAMURAI @ RIKEN-RIBF play a key role in the application of the SF method.